This invention relates to an imaging member comprising a substrate and an image layer comprising smectite clay particles intercalated with polyvinyl pyrrolidone and dispersed in polyethylene oxide. More particularly, the present invention relates to an ink jet image recording element, with a transparent image layer which yields printed images with excellent image quality and fast drying.
In the field of ink jet printing, it has been well known to employ one or more ink jet assemblies connected to a source of ink. Each ink jet is typically electromagnetically energized to emit uniform droplets of ink as a continuous stream or as individual droplets. The droplets are directed onto the surface of a moving web and controlled to form printed characters. In view of this technique, the quality of printing, using the ink jet recording process, is highly dependent on jet operation and the properties of the ink and particularly the surface characteristics of the imaging media and the type of coatings applied thereon. The ink must be capable of forming stable ink droplets under pressure and must readily emerge from the ink jet. Typically, the ink formulation is water based and contains organic addenda to prevent drying of the ink at the nozzle. However, the absorption of these inks by the recording sheet has been problematic, particularly in the area of multicolor printing where two or more ink drops may overlap on the surface of the recording sheet.
To ensure good image quality, the recording sheet must absorb the ink rapidly and, at the same time, immobilize the ink dye on the sheet surface. Good absorption reduces the ability of the ink to transfer to sheet handling rollers and other printer machine parts while immobilization of the ink dye ensures high optical density.
Unfortunately, imaging media with high absorbency draw the ink deeply into the media, which sacrifices optical density. Moreover, such recording sheets suffer from feathering and poor sharpness. In addition, high quality papers with low absorbency suffer from off-set because the ink is not absorbed rapidly and smearing often occurs.
Due to the advent of high quality, low cost, color ink jet printers and advancements in commercial papermaking, there is a demand for high color density and clear color tone resolutions. Paper for recording sheets used in such ink jet printing must rapidly absorb the ink and must be free from the flow-out of ink and from the danger of staining even if the paper is touched just after printing. Further, the diffusion of ink laterally on the recording sheet must be prevented in order to achieve high resolution without blurring. Thus, for obtaining color images, having good color density and resolution with good absorbing property ensuring fast drying, as well as optical brightness, is a critical need to be fulfilled.
In a typical ink jet recording or printing system, ink droplets are ejected from a nozzle at high speed towards a recording element or medium to produce an image on the medium. The ink droplets, or recording liquid, generally comprise a recording agent, such as a dye or pigment, and a large amount of solvent. The solvent, or carrier liquid, typically is made up of water, an organic material such as a monohydric alcohol or a polyhydric alcohol or a mixed solvent of water and other water miscible solvents such as a monohydric alcohol or a polyhydric alcohol.
The recording elements typically comprise a support or a support material having on at least one surface thereof an ink-receiving or image-forming layer. The elements include those intended for reflection viewing, which usually have an opaque or reflective support, and those intended for viewing by transmitted light, which usually have a transparent support.
U.S. Pat. Nos. 5,045,864; 5,084,338; 5,126,193; 5,126,194; 5,126,195; 5,139,867 and 5,147,717 teach about image forming layers containing polyvinyl pyrrolidone, polyalkylene oxide, and polyvinyl alcohol with different addenda, such as different surfactants, inert particles, and polyester particles of various specificity.
U.S. Pat. No. 5,624,482 describes a porous alumina hydrate layer on a substrate, which can cause gelling of water soluble polymer in the ink.
U.S. Pat. No. 5,660,622 describes a coating composition for ink jet recording sheets, which includes a combination of hydrated amorphous synthetic silica, a synthetic binder, a cationic agent, a leveling-flow modifier, a dispersing agent, and an optical brightener, resulting in a porous water-absorbing imaging layer.
U.S. Pat. No. 5,686,602 describes a cellulose polymer network cross-linked with metal ions having incorporated therein a colloidal sol containing metal oxide-hydroxide particles resulting in a microporous film.
U.S. Pat. No. 5,759,673 describes a two layered structure with a foamed undercoat of polymeric binder and an image receiving layer containing 50-90% amorphous silica.
U.S. Pat. No. 5,750,200 describes a two layered cast-coated structure with an image receiving layer of pigment and binder and a gloss-providing layer of pigment and latex.
U.S. Pat. No. 5,688,603 describes a two layered structure with an absorbing layer of water absorbent polymer and a cross-linkable polymer with a cross-linking agent, and an optically clear topcoat of hydroxycellulose, fluorocarbon surfactants and metal chelate.
U.S. Pat. No. 5,576.088 describes a two layered, cast-coated structure with an image receiving layer of pigment and binder and a gloss-providing layer of pigments of  less than 300 nm size (either colloidal silica or polystyrene beads) and styrene-butadiene latex.
U.S. Pat. No. 5,171,626 describes a two layered structure with aluminum oxide in both layers, but with the lower layer particle size being  less than 20 xcexcm and the upper layer particle size being  less than 70 xcexcm.
U.S. Pat. No. 5,560,996 describes a dye-receiving layer, comprising an intercalated compound capable of fixing water-soluble dyes to a printing paper due to the intercalation based on ion-exchange. The intercalated compounds are suggested to be montmorillonoids for water-soluble cationic dyes, and hydrotalcite-group minerals for water-soluble cationic dyes.
European Patent Application EP 0 732 218 A1 describes an ink-receiving layer comprising synthetic clay with or without any polymeric binder.
European Patent Application EP 0 709 221 A1 discloses an ink receptive coating containing polyvinyl pyrrolidone, an acrylic copolymer, and a quaternized acrylate copolymer hydroxyethyl cellulose and hydroxypropyl methyl cellulose, polyvinyl alcohol, and vinyl pyrrolidone copolymer.
European Patent Application EP 0 818 322 A1 discloses an ink jet recording sheet with a substrate impregnated or coated with a cationic compound, an ink-receiving layer containing pigment and a binder, and a gloss layer containing a polymer resin produced from ethylenically unsaturated monomers.
Although the related patent literature is replete with inventions, a great many problems still exist in the art. For example, the use of hydrophilic polymers as an imaging layer often provides a slow drying tacky surface not conducive for multiple stacking of printed sheets. Porous/microporous imaging layers can somewhat ameliorate the situation, but at a cost of substantially reducing the gloss of the substrate or xe2x80x9cqualityxe2x80x9d of the image. Additionally, such layers may not be completely haze-free for use in applications such as transparencies. Multiple layers are proposed for improved properties, but co-optimization of each functional layer, ensuring their compatibility as well as interlayer adhesion, and robust manufacturing of such imaging elements often pose a formidable challenge.
In general, the requirements for an image-recording medium or element for ink-jet recording are very demanding. It is well known that in order to achieve and maintain photographic-quality images on such an image-recording element, the recording element must:
(1) be readily wetted so there is no puddling, i.e., coalescence of adjacent ink dots, which leads to nonuniform density;
(2) exhibit no image bleeding;
(3) exhibit the ability to absorb high concentrations of ink and dry quickly to avoid elements blocking together when stacked against subsequent prints or other surfaces;
(4) provide a high level of gloss and be sufficiently insoluble in typical ink solvents to avoid development of differential gloss;
(5) exhibit no discontinuities or defects due to interactions between the support and/or layer(s), such as cracking, repellencies, comb lines and the like;
(6) not allow unabsorbed dyes to aggregate at the free surface causing dye crystallization, which results in bloom or bronzing effects in the imaged areas;
(7) be optimized image fastness to avoid fade from contact with water or radiation by daylight, tungsten light, or fluorescent light.
While a wide variety of different types of image-recording elements for use with ink jet ink devices have been proposed heretofore, there are many unsolved problems in the art and many deficiencies in the known products which have severely limited their commercial usefulness.
There remains a need for the development of an imaging member, with a haze-free, transparent, fast drying, non-tacky, glossy, smooth imaging layer capable of bearing photographic quality images with high optical density.
It is an object of the invention to provide an imaging member with an image layer that can provide photographic quality images with high optical density.
It is another object to provide an imaging member that can be recorded or printed in a typical ink jet recording or printing system.
It is a further object to provide an imaging layer that is smooth, non-tacky, fast-drying and haze free that can be used for reflective, as well as transparent imaging supports.
It is an additional object of the invention to provide a method of forming an image receiving layer with the aforesaid qualities.
These and other objects of the invention are accomplished by providing an imaging member comprising a substrate and an image layer comprising smectite clay particles intercalated with polyvinyl pyrrolidone and dispersed in polyethylene oxide.
The invention provides an imaging member capable of providing photographic quality images with exceptionally high optical density when the imaging member is printed in a typical ink jet printer.